1. Field of the Invention
One or more embodiments of the present invention relate to an image photographing device and method, and more particularly, to an image photographing device and method that can enhance image sensitivity.
2. Description of the Related Art
Recently, it has become popular for differing devices to be equipped with high-resolution cameras, such as digital personal assistants, digital cameras, and camera phones. Such devices with a high-resolution camera typically include a lens and an image sensor.
Here, the lens collects light reflected from a subject, and the image sensor detects the light collected by the lens and converts the detected light into an electrical image signal. Image sensors can be largely classified into image pickup tubes and solid-state image sensors. Major examples of the solid-state image sensors include a charge coupled device (CCD) and complementary metal oxide semiconductor (CMOS).
The image sensor included in the camera may include a color filter array (CFA) of color filters corresponding to pixels, respectively. Since the image sensor is sensitive to infrared light, an infrared filter is formed on the CFA to prevent image discoloration. As an example, the infrared filter, the CFA, and the image sensor can be manufactured as one module, with the infrared filter being separated a predetermined distance away from the image sensor, and the color filter array being stacked on the image sensor.
A primary color-based CFA and a complementary color-based CFA are two of the most widely used CFAs. The primary color-based CFA limits an incident light to any one of three primary colors, e.g., red, green and blue (RGB) as illustrated in FIG. 1. The complementary color-based CFA filters out a complementary color of an incident light using a complementary color filter composed of cyan, magenta and yellow, for example.
FIG. 1 illustrates an example of a green filter, and FIG. 2 illustrates an example of a magenta filter, which is a complementary color of green. In FIG. 1, since the incident light is limited, through the filtering, to green light, only ⅓ of the total light of the incident light is passed through the green filter. Hence, when the green filter, which is a primary color filter, is used, superior color reproducibility can be obtained, but there is a limit to enhancing sensitivity. In FIG. 2, green light, which is a complementary color of magenta, is filtered out from the incident light. Hence, ⅔ of the total light of the incident light is passed through the magenta filter. Hence, when the magenta filter is used, better sensitivity may be obtained than when the green filter of FIG. 1 is used, but color reproducibility is reduced.
Recently, the number of effective pixels included in a CMOS image sensor of a camera has increased in order to achieve higher resolutions. However, if the number of effective pixels is increased disproportionately with any increase in the size of the CMOS image sensor, the amount of light reaching each pixel becomes reduced, which, in turn, undermines sensitivity.
Japanese Patent Publication No. 2005-006066 discusses a color filter for a solid-state image pickup device. In this publication, the color filter includes RGB filters for enhancing color reproducibility and sensitivity and an infrared filter for filtering out infrared light. However, since the three-primary color filters are used to enhance color reproducibility, there is still a limit to enhancing sensitivity.